Antibiotics are a group of important medicins that treat and prevent bacterial infections of various types. Currently, more than 100 different antibiotics are available to treat a wide range of infections, from minor infections to life-threatening infections.
Antibiotic is a chemical compound created to destroy bacteria. It can be produced naturally or synthetically. The role of the antibiotic is to stop the reproduction of bacteria through different methods.
There are antibiotics that only block the bacteria's metabolism, allowing the immune system to destroy them, and antibiotics that aim to kill the bacteria. Also, the antibiotic can be used preventively, as for example to prevent the occurrence of infections, before some operations.
Bacteria are unicellular organisms in search of food sources; when they manage to pass the filters of the immune system, once they enter the body they begin to multiply, causing us, most often, different ailments.
How did the antibiotic come about?
It was the Scottish bacteriologist Alexander Fleming who discovered in 1928, by accident, the strange bacteria-killing properties of the "juice" secreted by a fungus of the Penicillium class. On his return from a two-week leave he found the culture of Staphylococci affected by Penicillium, which, fortunately, had arrived there from a laboratory one floor below. Fleming noticed that the bacteria he was studying was all over the culture medium, but not in the moldy area. Therefore, the "intruder" was responsible for inhibiting the growth of bacteria.
Do antibiotics also work against viruses?
Antibiotics do not work on viruses. Viruses are, in essence, a chain of DNA or RNA, without their own metabolism, considered not to be living organisms. There is nothing to destroy from an antibiotic perspective.
However, there are cases in which doctors can prescribe antibiotics even if the nature of the disease is viral. This happens because it is possible that the patient's body is so weakened that the doctor considers that an infection caused by bacteria is possible. Therefore, in certain situations, for preventive purposes, antibiotics can also be useful in viral diseases.
Antibiotic resistance of bacteria
One of the extremely serious problems facing humanity is the increase in the resistance of bacteria to existing antibiotics. Antibiotic resistance means either that the antibiotic no longer has any effect on the bacteria or that the effect is insufficiently strong to stop the disease. Bacteria become resistant to antibiotics not only because of humans, but sometimes it happens as a result of antibiotic attacks between different types of bacteria.
There are three ways of obtaining resistance to antibiotics. The first way is the spontaneous mutation of the bacterium. Most of the time, this mutation leads to the death of the bacterium, but there are cases when this mutation is beneficial, in the sense that it confers immunity to the administration of the antibiotic. Another way of immunization is the transfer of genetic information between bacteria, a non-immune bacterium, through the process called "conjunction", receives immunizing genetic material from another bacterium. Finally, the bacterium can acquire antibiotic resistance following an attack by a bacteriophage virus, which, if it does not kill it, can provide it with the genetic material necessary to survive in the fight against an antibiotic. Once immunity is obtained, the bacteria transfer it to future generations.
How quickly do antibiotics work and for what period should they be taken?
Of course, the basis is the doctor's advice. However, as a general idea, the antibiotic starts to take effect after about 24 hours. If after 72 hours from the administration of the first pill there are no visible signs of improvement in health, it is very possible that the antibiotic is not effective in combating the disease, requiring a new medical consultation and probably the prescription of another type of medication (or another type of antibiotic).
As a rule, the minimum period for which the antibiotic must be administered is 5 days. If you stop the treatment immediately when you seem to have recovered (which can happen, in the case of a sore throat, for example, only two days after taking the first pill), it is very possible that the bacteria remaining in body to be vigorous enough to multiply again and resume the attack against the body, the original symptoms returning.Bacteriologul scotian Alexander Fleming a descoperit în anul 1928 primul antibiotic natural, penicilina.
• Antibiotics do not act on viruses.
• Appropriate use of antibiotics is essential to reduce antibiotic resistance.
• Fleming predicted the rise of antibiotic resistance. Bacteria become resistant to antibiotics over time, which reduces their effectiveness to control infection.
• Antibiotics work either by killing bacteria or by stopping their growth.
Action of antibiotics
Antibiotic treatment aims to completely eliminate the pathogenic bacteria from the body. The objective of an antibiotic molecule is to reach the surface or inside the bacterial cell and to selectively target certain molecular or biological structures from its component, leaving the animal organism unaffected.
There are different types of antibiotics, which act in two ways:
• Kills bacteria (bactericidal effect) - such as penicillin. These antibiotics interfere with either the formation of the bacterial cell wall or its cell contents.
• They stop the growth of bacteria without destroying them (bacteriostatic effect) - such as tetracyclines.
• Due to the great diversity of antibiotics, there are a multitude of mechanisms of action by which they exert their neutralizing or toxic effect on bacterial organisms. The objective of an antibiotic molecule is to reach the surface or inside the bacterial cell and selectively target certain molecular or biological structures within them, leaving the animal host cells unaffected. In this case, as can be seen in the diagram on the right, antibiotics can act on the cell wall, cell membrane, nucleic acids, proteins or bacterial ribosomes.
• Also, through the mechanism they present, antibiotics can be part of two large classes, so they can have a bacteriostatic effect (inhibiting the growth of microorganisms, but without destroying them) or bactericidal (causing the death of bacterial cells), but there are examples of antibiotics that produce both effects.
The cell wall
• A relatively large number of antibiotics manifest their effect by blocking the synthesis, organization or final formation of the cell wall, especially at the binding points of peptidoglycan (which is its main component), but do not interfere at all with other intracellular components. Following the inhibition of the synthesis of the cell wall, changes occur in the intracellular composition of the microorganism, due to some changes in the osmotic pressure. As long as intracellular processes can take place, they try to compensate for the internal pressure created by the lack of a cell wall, but until the cell is destroyed. At the same time, the lack of the wall will allow other antibacterial agents to enter.
Some examples of antibiotics that act at the level of the cell wall are: all beta-lactam antibiotics (penicillins, cephalosporins, monobactams, carbapenems, by binding to the enzymes responsible for peptidoglycan synthesis), glycopeptide antibiotics (by preventing the binding of peptidoglycan layers) and bacitracin (by preventing transport of peptidoglycan precursors)
Cell membrane
Another category of antibiotics is that which can produce a direct or indirect damage (by inhibiting the synthesis of some constituent molecules) on the cell membrane, an effect that can be manifested both in bacteria and in some fungal species. Many of the molecules target membrane phospholipids, which are anionic lipid components, and will attract cationic antimicrobial peptides, leading to physical deformations. Examples of such peptides include polymyxins (polymyxin B and colistin, which increase membrane permeability through detergent-like action) and daptomycin (which binds to the membrane and causes membrane depolarization)
Nucleic acids
• Some antibiotics have an effect of blocking the synthesis of nucleic acid molecules (DNA, RNA), the function of ribosomes or the enzymes that participate in the synthesis of bacterial proteins, which leads to the formation of defective proteins. If we consider the synthesis of DNA- and RNA, there are several types of enzymes involved in their synthesis that can be inhibited. First, quinolones inhibit topoisomerase type II (DNA gyrase) and topoisomerase type IV, which are absolutely necessary for DNA replication, recombination, and DNA repair processes. The same mechanism of DNA gyrase inhibition is also shown by aminocoumarins (novobiocin).
• There may be other mechanisms through enzyme inhibition. Rifamycins, a class to which rifampicin belongs, bind to RNA polymerase, which has the effect of inhibiting the initiation of RNA synthesis. Another mechanism is that presented by nitroimidazoles and nitrofurans, which insert into the bacterial cell and are reduced under the action of bacterial nitroreductases to cytotoxic compounds that affect the structure of nucleic acids and proteins.
Ribosomes and protein synthesis
• Finally, most classes of antibiotics are able to inhibit the processes that take place at the level of the bacterial ribosome, which is structurally different from the eukaryotic one. Ribosomes are the organelles with a role in the synthesis of cellular proteins, so by disrupting its function, protein synthesis will either stop, or non-functional, aberrant proteins will be formed.
There are 10 classes of antibiotics:
• Penicillins They are also called beta-lactam antibiotics because they contain a beta-lactam nucleus in their molecule. Penicillins, cephalosporins, monobactams and carbapenems are included in this category. It acts by inhibiting the synthesis of the bacterial wall, having a bactericidal effect (kills bacteria).
• Cephalosporins have a bactericidal effect (destroy bacteria) and act similarly to penicillins
• Carbapenems They are structurally related to penicillins. They have the widest spectrum of action among beta-lactams. They are considered reserve antibiotics, for moderate/severe cases of infection. They are reserved as the last line of treatment, to prevent the development of resistance.
• Macrolides- Erythromycin was frequently used as an alternative to penicillin treatment
• Tetracyclines - They have a bacteriostatic effect (inhibits the growth of bacteria without destroying them).
• Quinolones- They have a bactericidal effect (they kill bacteria) and a wide spectrum of action.
• Lincomycins - They have a bacteriostatic effect
• Sulfonamides - They have a bacteriostatic effect (the association with trimethoprim makes them bactericidal) and a wide spectrum of action.
• Glycopeptides
• Aminoglycosides